The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > 47 - Current classic GM Trucks > The 1967 - 1972 Chevrolet & GMC Pickups Message Board

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 04-20-2017, 10:36 AM   #1
67farmtruck
Registered User
 
Join Date: Jul 2006
Location: Jamestown, ND
Posts: 18
Ballast Resistor vs. Resistor Wire - 67 250

What is the difference between a ballast resistor (ceramic block with two posts) and a resistor wire, and how do I know which I need? I read a bunch of threads and couldn't figure it out.

I do not see a ballast resistor on my firewall but I do have a cluster of wires emerging from a square black box right next to the choke cable.

I changed out the points, condensor, cap, rotor, and plugs, but no spark. Auto parts guy suggested replacing the resistor first and then the coil, but I don't seem to have a resistor. Could the resistor wire be bad, if in fact that's what I have?

Any advice appreciated!
67farmtruck is offline   Reply With Quote
Old 04-20-2017, 10:53 AM   #2
Shady Rascal
Senior Member
 
Shady Rascal's Avatar
 
Join Date: Feb 2016
Location: Weatherford Texas
Posts: 308
Re: Ballast Resistor vs. Resistor Wire - 67 250

You have a resistor wire. Check it with a voltmeter and see if it's still supplying voltage to your coil. The coil gets voltage through two sources. While the engine is cranking, coil voltage comes from the starter solenoid. When you let the key back to run, it comes through the resistance wire.
Shady Rascal is offline   Reply With Quote
Old 04-20-2017, 10:58 AM   #3
67farmtruck
Registered User
 
Join Date: Jul 2006
Location: Jamestown, ND
Posts: 18
Re: Ballast Resistor vs. Resistor Wire - 67 250

What exactly is the voltage check and what range of values would indicate a functioning vs. a faulty resistor wire?

With the key in run position, what 2 points do I check voltage across?

So if the coil gets voltage from the starter solenoid with the key in "start", and I'm not getting spark with the key in "start", then the resistor wire could not be the problem....?
67farmtruck is offline   Reply With Quote
Old 04-20-2017, 11:07 AM   #4
Shady Rascal
Senior Member
 
Shady Rascal's Avatar
 
Join Date: Feb 2016
Location: Weatherford Texas
Posts: 308
Re: Ballast Resistor vs. Resistor Wire - 67 250

Key on run, red lead of volt meter to the + terminal on the coil, black lead of voltmeter to a ground. You should see somewhere above 6 volts or so.
Shady Rascal is offline   Reply With Quote
Old 04-20-2017, 11:23 AM   #5
67farmtruck
Registered User
 
Join Date: Jul 2006
Location: Jamestown, ND
Posts: 18
Re: Ballast Resistor vs. Resistor Wire - 67 250

Much appreciated - I will check that at lunchtime!
67farmtruck is offline   Reply With Quote
Old 04-20-2017, 11:25 AM   #6
Shady Rascal
Senior Member
 
Shady Rascal's Avatar
 
Join Date: Feb 2016
Location: Weatherford Texas
Posts: 308
Re: Ballast Resistor vs. Resistor Wire - 67 250

You bet.

If you do have power to the coil, take a test light and hook it to ground and then put the point on the negative terminal of the coil. Now crank the engine and see if the light flashes.
Shady Rascal is offline   Reply With Quote
Old 04-20-2017, 12:15 PM   #7
RichardJ
Registered User
 
Join Date: Apr 2010
Location: So Cal
Posts: 733
Re: Ballast Resistor vs. Resistor Wire - 67 250

>>Key on run, red lead of volt meter to the + terminal on the coil, black lead of voltmeter to a ground. You should see somewhere above 6 volts or so<<

That would only be true if the engine stopped at a point when the distributor points happened to be closed.
Not much of a test. The test light will give better info, but what are you actually testing for?

Is this a NO START problem? What is the problem that you are trying to diagnose?

There is no electrical difference between a " (ceramic block with two posts) and a resistor wire". Both should have a resistance of 1.8 Ohms for a six cyl chevy distributor.
__________________
'67 GMC, 3/4 ton, 292, 4 spd
RichardJ is offline   Reply With Quote
Old 04-20-2017, 12:34 PM   #8
67farmtruck
Registered User
 
Join Date: Jul 2006
Location: Jamestown, ND
Posts: 18
Re: Ballast Resistor vs. Resistor Wire - 67 250

Yes, this is a no start (no spark) problem.

I had it running one day and the next day, no start and no spark.

Points, condensor, cap, rotor, wires, and plugs are all new. Coil is old and I was going to throw in a new one but the auto parts guy suggested checking the resistor first.
67farmtruck is offline   Reply With Quote
Old 04-20-2017, 01:36 PM   #9
geezer#99
Registered User
 
geezer#99's Avatar
 
Join Date: Aug 2009
Location: Bowser
Posts: 8,767
Re: Ballast Resistor vs. Resistor Wire - 67 250

Put an hei in it and eliminate the resistor wire and the jumper from the starter.
Plus a hotter spark, better idle etc etc..
geezer#99 is offline   Reply With Quote
Old 04-20-2017, 02:24 PM   #10
67farmtruck
Registered User
 
Join Date: Jul 2006
Location: Jamestown, ND
Posts: 18
Re: Ballast Resistor vs. Resistor Wire - 67 250

I have 4.8 volts from the coil positive to ground with the key in "run".

The test light flashes from coil negative to ground with the key to "start".

Eventually will put in an HEI but just want it running for a little while first (so my son can drive it to Prom - way better than renting a limo).

Suggested next steps?

Thanks for the input!
67farmtruck is offline   Reply With Quote
Old 04-20-2017, 02:45 PM   #11
HO455
Registered User
 
HO455's Avatar
 
Join Date: Feb 2016
Location: Portland Oregon
Posts: 1,537
Re: Ballast Resistor vs. Resistor Wire - 67 250

Have you checked to see if the rotor is turning? (I was unable once to get an engine to start that I had driven the day before and it ended up being a broken timing gear) How did you check for spark? Do the troubleshooting before buying any more parts. (With the quality of the parts today you may be adding a problem) Disconnect the power wire from the coil and measure the voltage to ground. As previously stated you should see 6-8 volts. If not I would check the voltage at the ignition switch. It should be 12 volts. If it is OK then it is probably the firewall connector. If no voltage or less than battery voltage the the switch is suspect number one.
If the voltage at the coil is good then pop the distributor cap and do a careful inspection. The points are just a grounding switch. If your gap is correct then look to see if the ground wire from the breaker plate is intact and securely connected at both ends. Is the wire from the coil good with no cuts or broken spots. If it all looks good disconnect the other wire on the coil and hook a multimeter to it and to ground. Then open and close the points manually. It you don't see a high and low reading on the meter try unhooking the condenser to see if it makes a difference. (You could have a shorted condenser). If the meter never shows conductivity then the points are not closing, the contacts are insulated some way, or maybe there is an open in the wiring. (Could be either the wire to the points or from the breaker plate) If the meter is always showing conductivity then the points are not opening, or the wire to the points is shorted to the case. If so disconnect it from the points and test again. If all this checks out then you may have a bad coil which is easiest to check by swapping a good one in.
I just saw your last post and your volts are pretty low I would concentrate on the power to the coil first. Check the volts at the ignition switch
__________________
Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help.
http://www.superiorperformancenw.com
1967 Burban the WMB,1991 S(stink)-10 Blazer,1969 GTO, 1970 Javelin, 1952 F1-3 Ford 4X4
If it breaks I didn't want it in the first place
The WMB http://67-72chevytrucks.com/vboard/s...d.php?t=698377
HO455 is offline   Reply With Quote
Old 04-20-2017, 03:10 PM   #12
67farmtruck
Registered User
 
Join Date: Jul 2006
Location: Jamestown, ND
Posts: 18
Re: Ballast Resistor vs. Resistor Wire - 67 250

Yes, the rotor turns.

I replaced the other ignition parts recently, although prior to the current problem, so I assumed they didn't suddenly fail.

I'll check the ignition switch voltage. This would be 12V coming out of the switch with the key in "run", right?
67farmtruck is offline   Reply With Quote
Old 04-20-2017, 08:28 PM   #13
HO455
Registered User
 
HO455's Avatar
 
Join Date: Feb 2016
Location: Portland Oregon
Posts: 1,537
Re: Ballast Resistor vs. Resistor Wire - 67 250

Yes it should be 12 volts( within a 1/2 volt of whatever the battery voltage is).
__________________
Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help.
http://www.superiorperformancenw.com
1967 Burban the WMB,1991 S(stink)-10 Blazer,1969 GTO, 1970 Javelin, 1952 F1-3 Ford 4X4
If it breaks I didn't want it in the first place
The WMB http://67-72chevytrucks.com/vboard/s...d.php?t=698377
HO455 is offline   Reply With Quote
Old 04-20-2017, 08:35 PM   #14
67farmtruck
Registered User
 
Join Date: Jul 2006
Location: Jamestown, ND
Posts: 18
Re: Ballast Resistor vs. Resistor Wire - 67 250

OK, so now I'm really confused.

I pulled the + wire off the coil - with the switch to "run" I had 12+ volts. So I figured the ignition switch is OK and with the other symptoms, I swapped out the coil.

Now I turn the key and I get I very short burst of power and then nothing. And now the + wire to the coil shows extremely low voltage with the key in "run".

Bad ignition switch after all? Or something else?
67farmtruck is offline   Reply With Quote
Old 04-20-2017, 10:01 PM   #15
67farmtruck
Registered User
 
Join Date: Jul 2006
Location: Jamestown, ND
Posts: 18
Re: Ballast Resistor vs. Resistor Wire - 67 250

=Can't be the points or condensor, can it? I have super low voltage at the + wire to my coil when it's disconnected from the coil. Points and condensor aren't even in that circuit, are they?

Seems like it must be either the ignition wiring or the switch. So I can run a wire from the unfused spot on the panel to the + on the coil with a ceramic ballast inline to bypass my wiring harness?

Appreciate all the insight and knowledge of you all.
67farmtruck is offline   Reply With Quote
Old 04-20-2017, 10:18 PM   #16
franken
Registered User
 
Join Date: Jun 2013
Location: Somewhere
Posts: 1,919
Re: Ballast Resistor vs. Resistor Wire - 67 250

At any moment the points are either open, closed or opening and closing (cranking/running) so you may get different readings.
If I recall, the points closing allows current to flow through the coil primary to ground. Opening collapses the electrical/magnetic field, inducing high voltage on the secondary side, causing spark.

The system was designed for 6V so when 12V came around, points got cooked so they introduced a resistance to limit current. Or so I've read... Note current is limited because on points open, you should read 12V at the coil side of the resistance wire. An open always reads source voltage.

I think I'd pull a plug ground it and check for spark.
You can also jump around the resistor wire w/ a not resistance wire temporarily.
I'd also measure battery voltage across the terminals. A charged battery is 12.6V or more. Load it by say turning on the likes for some seconds first. Less than 12.6V is a battery in need of a charge.
Finally, condensers (capacitors actually) are in there to reduce arcing and wear on the points. A bad condenser can cause weak/no spark because current flow isn't interrupted.
franken is offline   Reply With Quote
Old 04-20-2017, 10:23 PM   #17
HO455
Registered User
 
HO455's Avatar
 
Join Date: Feb 2016
Location: Portland Oregon
Posts: 1,537
Re: Ballast Resistor vs. Resistor Wire - 67 250

Quote:
Originally Posted by 67farmtruck View Post
=Can't be the points or condensor, can it? I have super low voltage at the + wire to my coil when it's disconnected from the coil. Points and condensor aren't even in that circuit, are they?

Seems like it must be either the ignition wiring or the switch. So I can run a wire from the unfused spot on the panel to the + on the coil with a ceramic ballast inline to bypass my wiring harness?

Appreciate all the insight and knowledge of you all.
Yes you can by pass the factory wiring that way. You will need to put a switch in so you can shut the engine off and de-energize the coil when parked. Be sure you tape off or otherwise insulate and secure the factory wire to the coil so it won't short out.
__________________
Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help.
http://www.superiorperformancenw.com
1967 Burban the WMB,1991 S(stink)-10 Blazer,1969 GTO, 1970 Javelin, 1952 F1-3 Ford 4X4
If it breaks I didn't want it in the first place
The WMB http://67-72chevytrucks.com/vboard/s...d.php?t=698377
HO455 is offline   Reply With Quote
Old 04-21-2017, 12:54 AM   #18
Gmc.guy
Registered User
 
Gmc.guy's Avatar
 
Join Date: Nov 2015
Location: Whitecourt Alberta
Posts: 457
Re: Ballast Resistor vs. Resistor Wire - 67 250

I had the same symptoms with my 74. I had pertronix and hei in this truck but I like to keep the points in a 6 cyl I found my resistor wire exposed and corroded in a few places. I replaced the resistor wire right from the bulkhead with a 14 or 12 I think and run to a ceramic resistor on the firewall. Also wired to the starter like stock. Definitely starts and idles way better. It was a Chrysler application and I want to say 1.6 or 1.8 ohm. It was 12$ compared to 6-12$ a foot for the resistor wire for 6 or 8 feet.
__________________
-Cody
69 GMC short fleet, 307,350,12 bolt;74 GMC short step 250,465,12 bolt;74 Chevy long fleet 350,350,12 bolt;84 Chevy long fleet 6.2,700r4, 10 bolt;81 blazer,85 cab, 250,400,10 bolts;chained 35's And about 15 parts trucks
08 Sierra crew (wife's ride) 14 Gmc crew DD
"I've never felt so Sasquatchian" - Johnny Test
Gmc.guy is offline   Reply With Quote
Old 04-21-2017, 01:04 AM   #19
RichardJ
Registered User
 
Join Date: Apr 2010
Location: So Cal
Posts: 733
Re: Ballast Resistor vs. Resistor Wire - 67 250

>>I pulled the + wire off the coil - with the switch to "run" I had 12+ volts.<<
As you should. You should get this same voltage with the + wire connected, but only when the points happen to be "OPEN".

Earlier you said, >>I have 4.8 volts from the coil positive to ground with the key in "run".<< Obviously when you read the 4.8V, the points happened to be closed.


>>Now I turn the key and I get I very short burst of power and then nothing.<<

POWER??????

>>I have super low voltage at the + wire to my coil when it's disconnected from the coil.<<

What super low voltage? Earlier you said you had 12+ volts.


>>Can't be the points or condensor, can it? <<

You stand a better chance of having a BAD, NEW Chinese made condenser, than having a GOOD 30 year old condenser.

Did you check the dwell when you installed your new points and then check the timing afterward?
__________________
'67 GMC, 3/4 ton, 292, 4 spd
RichardJ is offline   Reply With Quote
Old 04-24-2017, 10:43 PM   #20
67farmtruck
Registered User
 
Join Date: Jul 2006
Location: Jamestown, ND
Posts: 18
Re: Ballast Resistor vs. Resistor Wire - 67 250

Things keep getting worse.

I thought the resistor wire was the problem so I bypassed it with a wire from the unfused ignition port to the coil +, with an inline ceramic resistor. Now I have only +1.2 volts at my unfused ignition port with the key in "run". Previously I had +12.

Where is the power going? My battery is brand new and reads +12.6. Is my ignition switch bad?
67farmtruck is offline   Reply With Quote
Old 04-25-2017, 12:28 AM   #21
67farmtruck
Registered User
 
Join Date: Jul 2006
Location: Jamestown, ND
Posts: 18
Re: Ballast Resistor vs. Resistor Wire - 67 250

OK, so if I have 12V on the red wire, then my ignition switch is bad.

If I have <12V on the red wire, I have a bad connection somewhere between the battery and the ignition switch - bad bulkhead connection, fault in the starter solenoid, etc.....?
67farmtruck is offline   Reply With Quote
Old 04-25-2017, 08:09 AM   #22
LockDoc
The Original Thread Killer

 
LockDoc's Avatar
 
Join Date: Aug 2006
Location: Montezuma, Iowa
Posts: 16,706
Re: Ballast Resistor vs. Resistor Wire - 67 250

Quote:
Originally Posted by 67farmtruck View Post
What is the difference between a ballast resistor (ceramic block with two posts) and a resistor wire, and how do I know which I need? I read a bunch of threads and couldn't figure it out.

I do not see a ballast resistor on my firewall but I do have a cluster of wires emerging from a square black box right next to the choke cable.

I changed out the points, condensor, cap, rotor, and plugs, but no spark. Auto parts guy suggested replacing the resistor first and then the coil, but I don't seem to have a resistor. Could the resistor wire be bad, if in fact that's what I have?

Any advice appreciated!

Did you adjust the points gap when you installed them or just put them in and tightened down the screw? What gap setting did you use?

LockDoc
__________________
Leon

Locksmith, Specializing In Antique Trucks, Automobiles, & Motorcycles
LockDoc is online now   Reply With Quote
Old 04-25-2017, 08:37 AM   #23
67farmtruck
Registered User
 
Join Date: Jul 2006
Location: Jamestown, ND
Posts: 18
Re: Ballast Resistor vs. Resistor Wire - 67 250

Yep, I gapped the points to .019 and tightened them down. Double checked nothing moved in there when the troubles started, too.

Where is the best place to find enough exposed wire or connector to check the red and other ignition wires? Back of the ignition switch or somewhere else?
67farmtruck is offline   Reply With Quote
Old 04-25-2017, 11:24 AM   #24
LockDoc
The Original Thread Killer

 
LockDoc's Avatar
 
Join Date: Aug 2006
Location: Montezuma, Iowa
Posts: 16,706
Re: Ballast Resistor vs. Resistor Wire - 67 250

-
Try hooking a wire from the positive post on the battery to the coil and see if the truck will start. (If it starts you will have to shut it down by unhooking the wire from the battery) If you don't have spark then, the problem is in the coil or distributor.

LockDoc
__________________
Leon

Locksmith, Specializing In Antique Trucks, Automobiles, & Motorcycles
LockDoc is online now   Reply With Quote
Old 04-25-2017, 09:32 PM   #25
67farmtruck
Registered User
 
Join Date: Jul 2006
Location: Jamestown, ND
Posts: 18
Re: Ballast Resistor vs. Resistor Wire - 67 250

So the red wire into my ignition switch is +12 and all the others coming out of the switch are like +1.5 with the key in "run".

Replace ignition switch?
67farmtruck is offline   Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 09:46 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Copyright 1997-2013 67-72chevytrucks.com